How Dense Are The Planets? - Universe Today Universe Today How Dense Are The Planets? Article Updated: 18 Feb , 2016 by Matt Williams The eight planets of our Solar System vary widely, not only in terms of size, but also in terms of mass and density (i.e. its mass per unit of volume). For instance, the 4 inner planets – those that are closest to the Sun – are all terrestrial planets , meaning they are composed primarily of silicate rocks or metals and have a solid surface. On these planets, density varies the farther one ventures from the surface towards the core, but not considerably. By contrast, the 4 outer planets are designated as gas giants (and/or ice giants) which are composed primarily of of hydrogen, helium, and water existing in various physical states. While these planets are greater in size and mass, their overall density is much lower. In addition, their density varies considerably between the outer and inner layers, ranging from a liquid state to materials so dense that they become rock-solid. Density also plays a vital role in determining a planet’s surface gravity and is intrinsic to understanding how a planet formed.

After the formation of the Sun at the center of our Solar System, the planets were formed from a protoplanetary disc . Whereas the terrestrial planets resulted from dust grains in the inner Solar System, planets in the outer Solar System accreted enough matter for their gravity to hold on to the nebula’s leftover gas. The Solar System. Image Credit: NASA The more gas they held onto, the larger they became. And the larger they became, the more matter they would accumulate, until such tie that they reached a critical point. Whereas the gas giants of Jupiter and Saturn grew exponentially, the ice giants (Uranus and Neptune), with only a few Earth masses of nebular gas, never reached that critical point. In all cases, density is measured as the number of grams per cubic cm (or g/cm³). Density of Mercury: Ad a terrestrial planet, Mercury is composed of metals and silicate material.

Mercury’s mean density is the second-highest in the Solar System, which is estimated to be 5.427 g/cm3 – only slightly less than Earth’s density of 5.515 g/cm3.However, if the effects of gravitational compression – in which the effects of gravity reduce the size of an object and increases its density – then Mercury is in fact more dense than Earth, with an uncompressed density of 5.3 g/cm³ compared to Earth’s 4.4 g/cm³. These estimates can be also used to infer details of its inner structure. Compared to Earth, Mercury is much smaller, which is why it inner regions are subject to less in the way of compression. Therefore, its high density is believed to be the result of a large, and iron-rich core. All told, metals like iron and nickel are believed to make up 70% of the planet’s mass (higher than any other planet), while silicate rock accounts for just 30%. Internal structure of Mercury: 1. Crust: 100–300 km thick 2. Mantle: 600 km thick 3. Core: 1,800 km radius.

Credit: MASA/JPL Several theories for this have been suggested, but the predominant one claims that Mercury had a thicker silicate crust earlier in its history. This crust was then largely blown off when a large planetesimal collided with the planet. Combined with its size and mass, Mercury has a surface gravity of 3.7 m/s2, which is the equivalent of 0.38 of Earth’s gravity (aka. 1 g). Density of Venus: The second planet from our Sun, as well as the second-closest terrestrial planet, Venus has a mean density of 5.243 g/cm3. Again, this is very close to Earth’s own density. And while much remains unknown about Venus’ geology and seismology, astronomers have an idea of Venus’ composition and structure based on comparative estimates of its size, mass and its density. In short, it is believed that Venus’ makeup and internal structure are very similar to Earth’s, consisting of a core, a mantle, and a crust. Also like Earth, the interior is though to be composed of iron-rich minerals, while silicate minerals make up the mantle and crust.

The slightly smaller size of Venus also means pressures are 24% lower in its deep interior than Earth’s. The internal structure of Venus – the crust (outer layer), the mantle (middle layer) and the core (yellow inner layer). Credit: Public Domain Because Venus and Earth have been cooling at about the same rate, it is believed that Venus’ core must be at least partially liquid. However, the lack of a magnetosphere around Venus has led scientists to question this, with some claiming that the core must be uniform in temperature, while others insist it is fully cooled and solid. Some has gone so as far as to suggest that it has no core. Density of Earth: Earth has the highest density of any planet in the Solar System, at 5.514 g/cm3. This is considered the standard by which other planet’s densities are measured. In addition, the combination of Earth’s size, mass and density also results in a surface gravity of 9.8 m/s². This is also used as a the standard (one g) when measuring the surface gravity of other planets. Like the other terrestrial planets, Earth’s interior is divided into layers which are distinguished by their chemical or physical (rheological) properties.

These layers consist of a core composed of iron and nickel, an upper and lower mantle composed of viscous silicate materials, and a crust composed of solid silicate materials. Artist’s impression of the Earth’s interior, which includes the upper and lower mantle, and the inner and outer core. Credit: Huff Post Science However, unlike the other terrestrial planets, Earth’s core region is divided into a solid inner core and a liquid outer core. The inner core measures an estimated 1220 km and is composed of iron and nickel, while the outer core extends beyond it to a radius of about 3,400 km. The outer core also rotates in the opposite direction of the Earth’s rotation, which is believed to be the source of the Earth’s magnetosphere. Like all planet’s, this density increases the closer one gets to the core, reaching an estimated 12,600–13,000 kg/m3 in the inner core. Density of Mars: As a terrestrial planet, Mars is also divided into layers that are differentiated based on their chemical and physical properties – a dense metallic core, a silicate mantle and a crust.

The planet’s overall density is lower than that of Earth’s, estimated at 3.933 g/cm³, and this density increases the closer one gets to the core. Like Earth, this is due to the fact that the core is composed of iron and nickel, while the mantle is made up of silicate materials. Current models of its interior imply a core region about 1,794 ± 65 kilometers (1,115 ± 40 mi) in radius, consisting primarily of iron and nickel with about 16–17% sulfur. Compared to Earth’s crust – which averages 40 km (25 mi) in thickness – the average thickness of Mars’ crust is about 50 km (31 mi), with a maximum thickness of 125 km (78 mi). Between it’s size, mass, and density, Mars has a surface gravity of about 3.711 m/s² – which works out to 0.38 g. Density of Jupiter: As a gas giant (aka. composed largely of gaseous and liquid matter) Jupiter has a lower mean density than any of the terrestrial planets.

However, at 1.326 g/cm3, it is also the second-most dense of the gas giants. Despite their incredible size and mass, the lower density is due to them being largely composed of noble gases, which are maintained in states ranging from gaseous to solid. Jupiter’s internal structure and composition. (Image Credit: Kelvinsong/Wikipedia Commons In addition, this density ranges considerably between its outer gaseous layers and its core, which is believed to be composed of rock and surrounded by a layer of metallic hydrogen. In the outermost layer, which are made up of elemental hydrogen and helium, the density of the materials is less than that of water – 0.0002 g/cm³ compared to 1 g/cm³ of water. Beneath that, where the planet’s hydrogen are in a liquid state, the density rises to roughly 0.5 g/cm³ and increases to 1 g/cm³ at the boundary with the layer composed of metallic hydrogen. The layer metallic hydrogen, meanwhile, has an estimated density of 4 g/cm³ – i.e. around the same as Mars.

And in the core, who’s composition is still the subject of speculation, the density rises to 25 g/cm³. Thought its average density is lower than that of the terrestrial planets, Jupiter’s overall size, mass, and the amount of material it packs into it frame makes for some powerful gravity. Measured from its “surface” (which in this case means its cloudtops), Jupiter’s gravity is over two and a hlaf times that of Earth – 24.79 m/s2, or 2.528 g. Density of Saturn: At 0.687 g/cm3, Saturn is the least dense of the gas giants. In fact, it’s mean density is actually lower than that of water, which means that if it were possible to place the planet into a tub of water, it would float. But as with Jupiter and the other giants, this density ranges considerably from the plant’s exterior (which is composed of elemental hydrogen and helium) to its core (which is again believed to be rocky, and surrounded by metallic hydrogen). Diagram of Saturn’s interior.

Credit: Kelvinsong/Wikipedia Commons Owing to its greater size but lower density than terrestrial planets, Saturn’s surface gravity (again, measured from its cloudtops) is just slightly higher than that of Earth’s -10.44 m/s² or 1.065 g. Density of Uranus: With a mean density of 1.27 g/cm3, Uranus is the second-least dense of the gas giants, after Saturn. Its slightly higher density is due to its composition, which consists primarily of various volatile ices – such as water, ammonia, and methane – in addition to gases like hydrogen and helium. For this reason, Uranus (and Neptune) are often referred to as “ice giants” to differentiate them from Jupiter and Saturn. The standard model of Uranus’s structure is that it consists of three layers. Like the other giants, this includes a rocky core and an outer layer of hydrogen and helium. But in Uranus’ case, these layers are connected by an icy mantle in the middle rather that one made up of liquid hydrogen. The presence of methane in its atmosphere is also what gives Uranus’ its particular hue.

Uranus’ overall size, mass, and density also mean that its surface gravity is less than that of Earth’s. All told, it works out to 8.69 m/s², which is equivalent to 0.886 g. Diagram of the interior of Uranus. Credit: Public Domain Density of Neptune: Neptune’s mean density is 1.638 g/cm³, making it the most dense of any of the giants. Like Uranus, its is composed of higher concentrations of volatiles relative to Jupiter and Saturn. Also like Uranus, its interior is differentiated between a dense core consisting of silicates and metals, a mantle consisting of water, ammonia and methane ices, and an atmosphere consisting of hydrogen, helium, and methane gas. The higher concentrations of methane in Neptune’s atmosphere is why it is darker in hue than Uranus. And between its size, mass and density, Neptune has a surface gravity of 11.15 m/s2 – which is the equivalent of 1.14 g. As you can see, the densities of the Solar planets varies widely.

Whereas those that are closer to the Sun are terrestrial and quite dense, those that inhabit the outer Solar System are largely gaseous and liquid, and are therefore less dense on average. If you are looking for more information, check out NASA’s Solar System exploration page , and here’s a link to NASA’s Solar System Simulator . Astronomy Cast has episodes on all the planets including Episode 49: Mercury , Planets - Zoom Astronomy Your age on the Planets The Planets (plus the Dwarf Planet Pluto) Our solar system consists of the sun, eight planets, moons, many dwarf planets (or plutoids), an asteroid belt, comets, meteors, and others. The sun is the center of our solar system ; the planets, their moons, a belt of asteroids , comets , and other rocks and gas orbit the sun. The eight planets that orbit the sun are (in order from the sun): Mercury , Venus , Earth , Mars , Jupiter , Saturn , Uranus , Neptune . Another large body is Pluto , now classified as a dwarf planet or plutoid. A belt of asteroids (minor planets made of rock and metal) lies between Mars and Jupiter.

These objects all orbit the sun in roughly circular orbits that lie in the same plane, the ecliptic (Pluto is an exception; it has an elliptical orbit tilted over 17° from the ecliptic). Easy ways to remember the order of the planets (plus Pluto) are the mnemonics: "My Very Excellent Mother Just Sent Us Nine Pizzas" and "My Very Easy Method Just Simplifies Us Naming Planets" The first letter of each of these words represents a planet - in the correct order. The largest planet is Jupiter. It is followed by Saturn, Uranus, Neptune, Earth, Venus, Mars, Mercury, and finally, tiny Pluto (the largest of the dwarf planets). Jupiter is so big that all the other planets could fit inside it. The Inner Planets vs. the Outer Planets The inner planets (those planets that orbit close to the sun) are quite different from the outer planets (those planets that orbit far from the sun). The inner planets are: Mercury, Venus, Earth, and Mars. They are relatively small, composed mostly of rock, and have few or no moons. The outer planets include: Jupiter, Saturn, Uranus, Neptune, and Pluto (a dwarf planet).

They are mostly huge, mostly gaseous, ringed, and have many moons (again, the exception is Pluto, the dwarf planet, which is small, rocky, and has four moons). Temperatures on the Planets Generally, the farther from the Sun, the cooler the planet. Differences occur when the greenhouse effect warms a planet (like Venus) surrounded by a thick atmosphere. Density of the Planets The outer, gaseous planets are much less dense than the inner, rocky planets. The Earth is the densest planet. Saturn is the least dense planet; it would float on water. The Mass of the Planets Jupiter is by far the most massive planet; Saturn trails it. Uranus, Neptune, Earth, Venus, Mars, and Pluto are orders of magnitude less massive. Gravitational Forces on the Planets The planet with the strongest gravitational attraction at its surface is Jupiter. Although Saturn, Uranus, and Neptune are also very massive planets, their gravitational forces are about the same as Earth. This is because the gravitational force a planet exerts upon an object at the planet's surface is proportional to its mass and to the inverse of the planet's radius squared.

A Day on Each of the Planets A day is the length of time that it takes a planet to rotate on its axis (360°). A day on Earth takes almost 24 hours. The planet with the longest day is Venus ; a day on Venus takes 243 Earth days. (A day on Venus is longer than its year; a year on Venus takes only 224.7 Earth days). The planet with the shortest day is Jupiter ; a day on Jupiter only takes 9.8 Earth hours! When you observe Jupiter from Earth, you can see some of its features change. The Average Orbital Speed of the Planets As the planets orbit the Sun , they travel at different speeds. Each planet speeds up when it is nearer the Sun and travels more slowly when it is far from the Sun (this is Kepler's Second Law of Planetary Motion ). The Planets in Our Solar System Planet (or Dwarf Planet) In 2005, a large object beyond Pluto was observed in the Kuiper belt. A few astronomers think that there might be another planet or companion star orbiting the Sun far beyond the orbit of Pluto. This distant planet/companion star may or may not exist.

The hypothesized origin of this hypothetical object is that a celestial object, perhaps a hard-to-detect cool, brown dwarf star (called Nemesis ), was captured by the Sun's gravitational field. This planet is hypothesized to exist because of the unexplained clumping of some long-period comet's orbits. The orbits of these far-reaching comets seem to be affected by the gravitational pull of a distant, Sun-orbiting object. Planet Activities and Quizzes The Solar System The Solar System Our Solar System is an amazing place. Not only is it home to eight planets, it also hold several dwarf planets, hundreds of moons, and thousands of stars and asteroids. The eight planets in our Solar System are Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus, and Neptune. These planets orbit the Sun. Here is a funny song to help you remember the planets The Sun The Sun is the center of our Solar System. It is because of the Sun that our solar system gets its name. Sol is the Roman name for Sun. The Sun is the largest object within the Solar System - it makes up more than 95% of all the matter!

It is because of the Sun's large size that the rest of the objects within the Solar System orbit around it. The Sun is very, very hot. It is 10,000 degrees Fahrenheit on its surface. Mercury Mercury is the closest planet to the Sun, making it the first planet in the Solar System. It is named after the Roman messenger god. In mythology, the god was known for being quick - Mercury is the fastest of all the planets to orbit the Sun, because it has the smallest route it has to take! Mercury can occasionally be seen from Earth Mercury is the second densest planet in the Solar System It is mainly made up of iron There is no atmosphere on Mercury Despite its fast trip around the Sun, Mercury's revolution is very slow - one day on Mercury equals about 59 days on Earth! Venus Venus is the second planet from the Sun. It is named after the Roman goddess of beauty and love. Venus is almost the same size as Earth, but other than size the two planets are very different! Fun Facts about Venus Venus appears to be the brightest planet in the sky due to the reflection of the Sun from its clouds, and its closeness to Earth Venus has an incredibly thick atmosphere.

This makes it the hottest of the inner planets Venus rotates East to West Venus is covered in volcanoes Venus does not have any moons Earth Earth is the only known planet that has any life forms in the Solar System. It is the third planet from the Sun. It is the only planet that is not named after a god. Most of the Earth is covered in water - 70%! Earth has a thin atmosphere, that protects us from dangerous gasses and heat in space Earth is the largest of the inner planets Air, water, and land make up the Earth Earth's axis is tilted at 23.5 degrees This a video showing the many different life forms that Earth has Mars Mars is the fourth planet from the Sun. Named for the Roman god of war, it is also known as the "Red Planet". It is the last of the inner planets. Temperatures on Mars are very similar to temperatures on Earth It is believed that Mars once had water on its surface Mars is called the red planet because its surface is covered in red dust The largest volcano in the Solar System is on Mars. It is called Olympus Mons Mars has two small moons Jupiter Jupiter is the first of the outer planets, and the fifth planet from the Sun.

It is named for the king of the Roman gods. It is the largest of all of the planets. Fun Facts about Jupiter Jupiter is best known for its "Great Red Spot" - a mass of hurricanes that have been storming for hundreds of years. The spot is larger in size than that of Earth Jupiter is made up of gasses - there is no solid surface on it Jupiter is so big; Earth could fit inside of it more than 1,000 times! Jupiter has over 50 moons. Four of these moons are as big as planets Jupiter has the most active volcanic activity in the Solar System Learn more about the Great Red Spot! Saturn Saturn is the sixth planet from the Sun. It is named for the Roman god of agriculture. It is most well known for its highly visible rings. Other Features of the Solar System There are many other exciting elements in the Solar System. Here are a few. Asteroids Asteroids are rocky bodies in the Solar System that are too small to be considered actual planets. In between Mars and Jupiter lies the Asteroid Belt, containing well over 90,000 asteroids. Comets Comets are ice and rock that grow tails the closer they get to the sun.

The hotter they get, the longer this "tail" becomes. The sunlight makes comets glow, which causes them to be visible on Earth. Dwarf Planets Dwarf planets are bodies that orbit the sun that are not considered large enough to be actual planets. The most famous dwarf planet is Pluto, which was considered an actual planet up until 2006. Satellites Satellites are machines put into the Solar System by scientists in order to find out more about the Solar System, and what is in it. These machines take pictures, perform experiments, take data, and much, much more. Without them, we wouldn't have the vast amount of information that we have today. Summary The Solar System is a fascinating place. Each of the eight planets have their own unique features, but are also similar in some ways - much like people! It is amazing to think that the Solar System has been around for more than 4.6 billions years. Each of the eight planets orbits the sun in the same direction, and in their own time. We have so much more we can learn about the Solar System, and so much we have learned already today. sit this page to learn more interesting facts about the Solar System!

Want to get an idea of how far apart the planets are? Click here! Resources Our Solar System. Retrieved from Solar System. Retrieved from BBC Solar System - Earth orbits in the Goldilocks zone Listen now 45 min Melvyn Bragg examines our knowledge of the planets in both our and other solar systems. Melvyn Bragg discusses our knowledge of the planets in both our and other solar systems. What causes them to form and what is the likelihood of there being another with properties similar to Earth’s? About Earth Earth, otherwise known as the world,[n 5] (Greek: Γαῖα Gaia;[n 6] Latin: Terra) is the third planet from the Sun and the only object in the Universe known to harbor life. It is the densest planet in the Solar System and the largest of the four terrestrial planets. According to radiometric dating and other sources of evidence, Earth formed about 4.54 billion years ago. Earth's gravity interacts with other objects in space, especially the Sun and the Moon.

During one orbit around the Sun (one year), Earth rotates about its axis, creating 365.26 days.[n 7] Earth's axis of rotation is tilted, producing seasonal variations on the planet's surface. Earth has only one moon. The gravitational interaction between the Earth and Moon causes ocean tides, stabilizes the Earth's orientation on its axis, and gradually slows its rotation. Earth's lithosphere is divided into several rigid tectonic plates that migrate across the surface over periods of many millions of years. Seventy-one percent of Earth's surface is covered with water. The remaining 29% is land consisting of continents and islands that together have many lakes, rivers and other sources of water that contribute to the hydrosphere. The majority of Earth's polar regions are covered in ice, including the Antarctic ice sheet and the sea ice of the Arctic ice pack. Earth's interior remains active with a solid iron inner core, a liquid outer core that generates the Earth's magnetic field, and a convecting mantle that drives plate tectonics.

Within the first billion years of Earth's history, life appeared in the oceans and began to affect the Earth's atmosphere and surface, leading to the proliferation of aerobic and anaerobic organisms. Some geological evidence indicates that life may have arisen as much as 4.1 billion years ago. Since then, the combination of Earth's distance from the Sun, physical properties, and geological history have allowed life to evolve and thrive. In the history of the Earth, biodiversity has gone through long periods of expansion, occasionally punctuated by mass extinction events. Over 99% of all species that ever lived on Earth are extinct. Estimates of the number of species on Earth today vary widely; most species have not been described. Over 7.3 billion humans live on Earth and depend on its biosphere and minerals for their survival. Humanity has developed diverse societies and cultures; politically, the world is divided into about 200 sovereign states. Mercury In Roman mythology Mercury is the god of commerce, travel and thievery, the Roman counterpart of the Greek god Hermes, the messenger of the Gods. The planet probably received this name because it moves so quickly across the sky.

Mercury has been known since at least the time of the Sumerians (3rd millennium BC). The IAU changed the definition of "planet" so that Pluto no longer qualifies. There are officially only eight planets in our solar system. Of course this change in terminology does not affect what's actually out there. In the end, it's not very important how we classify the various objects in our solar system. What is important is to learn about their physical nature and their histories. Planet Order from the Sun; Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus and Neptune Our knowledge of our solar system is extensive but it is far from complete. Some of the worlds have never even been photographed up close. The Nine Planets is an overview of what we know today. We are still exploring, much more is still to come: We shall not cease from exploration, and the end of all our exploring will be to arrive where we started and know the place for the first time. -- T. S.

Eliot Planets in our solar system | Sun and solar system | Solar System for children | 8 planets elearnin - YouTube Planets in our solar system | Sun and solar system | Solar System for children | 8 planets elearnin Want to watch this again later? Sign in to add this video to a playlist. Need to report the video? Sign in to report inappropriate content. The interactive transcript could not be loaded. Loading... Rating is available when the video has been rented. This feature is not available right now. Please try again later. Published on Sep 5, 2013 Planets in our solar system | Sun and solar system | Solar System for children | elearnin The Solar System consists of the Sun and its planetary system of eight planets, their moons, and other objects including asteroids and meteors. Our planet Earth is one among the eight planets that revolve around the Sun. It's called solar system because the word solar means relating to the sun. Since Sun is the centre most part of this system, it is called solar system. Objects seem to smaller in size when seen from a great distance but are very huge and large in reality.

Similarly, the moon and stars are very big and huge in size, but appear to be smaller in size to our eyes because they are very very far away from the Earth, where we live. The distance between the objects in the solar system is so large that these numbers would run into millions and billions of kms. Hence they are measured with a specific unit called light year. One light year is exactly 9460730472580800 mts. Sun is 149,600,000 km away from earth. Sun is very far from the Earth. That is the reason why sun looks smaller in size. Solar system is the family of the sun. Sun is very big compared to the moon, probably around 400 times bigger. Sun is also a star but, remember, it's not the biggest star in the Universe. There are lots of stars present in the universe which are very far away from the sun, some of them about thousands of light years away. That is why stars look like dots in the night sky. Sun is like a ball of fire. The sunlight from the sun takes about 8.5 minutes to reach the surface of the earth.

Sun is the center of the solar system and all the planets revolve around the sun in orbits. Orbit is a curved path of an object around a point in space. Orbit means moving around in Roman. Earth is one of the planets in the solar system and takes exactly 365.25 days to revolve around the sun. Earth also rotates around its own axis in 24 hours or 1 day. Just like Earth every planet rotates on its own axis and revolves around the Sun. Mercury: Mercury is the smallest of all planets, it is every hot as it is the closest to the sun, hence no living being can live on this planet. Mercury was named after a roman god Mercury who is the fast flying messenger. Mercury takes only 88 days to revolve around the sun, which makes it the fastest revolving planet around the sun. Venus: Venus is the second closest planet to the Sun. Venus is visible in morning and evening as the brightest star from earth. Venus takes about 244.7 days to orbit around the sun and is named after the roman goddess of love and beauty. Earth: Our planet Earth is the third closest planet to the Sun.

It is blue in color as there is lot of water present on the surface of earth. Water constitutes to about 70% of entire surface on the earth. Unlike Earth, moon is not a planet. It is a natural satellite of earth and it revolves around the earth. Satellite is a smaller body which rotates around another rotating body. Earth is the only planet which has animals, trees and human beings. Mars: Mars is called the red planet because it's red in color. This red color is due to the presence of a chemical called iron oxide. Mars is named after the roman god of war. It two moons that in turn revolve around it. Jupiter: Jupiter is the biggest and largest planet of the solar system and is named after roman god Jupiter. Jupiter is 317 times the mass of Earth. Jupiter may have all the rocky core of the heavier elements making it the biggest and the heaviest planet. Outer atmosphere of Jupiter is divided into several bands at different latitudes, resulting in storms. Jupiter has around 67 moons revolving around it. These are natural satellites of Jupiter. Saturn: Saturn is the only planet has rings around it. Saturn is named after the roman god for agriculture.

Saturn has just over 95 times mass as compared to the earth. The rings around the Saturn are mostly composed of the ice particles and some rocky debris and some dust. Saturn has around 62 moons revolving around it. Uranus: Uranus is similar to Neptune and is named after the Greek god of sky Ouranos. It has around 27 natural satellites revolving around it. The Uranus is a unique as compared to the other planets because of the fact that its axis of rotation is tilted sideways unlike the other planets. Its looks bluish-green in color because the atmosphere of Uranus is very cold and cloudy. Neptune: This is the farthest planet from the sun. It is about 17 times the size of earth. Neptune is light blue in color because it is the coldest of all planets. Neptune is the densest of all planets. It is named after the roman god for sea. There was another planetary object called Pluto which was the 9th planet but is no more considered a planet because Pluto and its moons are now considered to be a region.This region extends from the orbit of Neptune.

Category Solar System Planets: Order of the 8 (or 9) Planets Solar System Planets: Order of the 8 (or 9) Planets By Robert Roy Britt | January 22, 2016 12:35pm ET MORE The planets of the solar system as depicted by a NASA computer illustration. Orbits and sizes are not shown to scale. Credit: NASA Ever since the discovery of Pluto in 1930, kids grew up learning about the nine planets of our solar system. That all changed starting in the late 1990s, when astronomers began to argue about whether Pluto was a planet. In a highly controversial decision , the International Astronomical Union ultimately decided in 2006 to call Pluto a “dwarf planet,” reducing the list of “real planets” in our solar system to eight. However, astronomers are now hunting for another planet in our solar system, a true ninth planet , after evidence of its existence was unveiled on Jan. 20, 2016. The so-called "Planet Nine," as scientists are calling it, is about 10 times the mass of Earth and 5,000 times the mass of Pluto.

[ Solar System Pictures: A Photo Tour ] If you insist on including Pluto , then that world would come after Neptune on the list; Pluto is truly way out there, and on a wildly tilted, elliptical orbit (two of the several reasons it got demoted). Interestingly, Pluto used to be the eighth planet, actually. More on that below. Terrestrial planets The inner four worlds are called “ terrestrial planets ,” because, like Earth, their surfaces are all rocky. Pluto, too, has a solid surface (and a very frozen one) but has never been grouped with the four terrestrials. Jovian planets The four large outer worlds — Jupiter, Saturn, Uranus, and Neptune — are known as the “Jovian planets” (meaning “Jupiter-like”) because they are all huge compared to the terrestrial planets, and because they are gaseous in nature rather than having rocky surfaces (though some or all of them may have solid cores, astronomers say).

According to NASA , "two of the outer planets beyond the orbit of Mars — Jupiter and Saturn — are known as gas giants; the more distant Uranus and Neptune are called ice giants." This is because, while the first two are dominated by gas, while the last two have more ice. All four contain mostly hydrogen and helium. Dwarf planets The IAU definition of a full-fledged planet goes like this: A body that circles the sun without being some other object's satellite, is large enough to be rounded by its own gravity (but not so big that it begins to undergo nuclear fusion, like a star) and has "cleared its neighborhood" of most other orbiting bodies. Yeah, that’s a mouthful. The problem for Pluto, besides its small size and offbeat orbit, is that it shares its space with lots of other objects in the Kuiper Belt , beyond Neptune. Still, the demotion of Pluto remains controversial . The IAU planet definition puts other small, round worlds in the dwarf planet category, including the Kuiper Belt objects Eris , Haumea , and Makemake . Also now a dwarf planet is Ceres , a round object in the Asteroid Belt between Mars and Jupiter.

Ceres was actually considered a planet when discovered in 1801 and then later deemed to be an asteroid. Some astronomers like to consider Ceres as a 10th planet (not to be confused with Nibiru or Planet X ), but that line of thinking opens up the possibility of there being 13 planets, with more bound to be discovered. The planets Below is a brief overview of the eight primary planets in our solar system , in order from the inner solar system outward: Mercury The closest planet to the sun, Mercury is only a bit larger than Earth's moon. Its day side is scorched by the sun and can reach 840 degrees Fahrenheit (450 Celsius), but on the night side, temperatures drop to hundreds of degrees below freezing. Mercury has virtually no atmosphere to absorb meteor impacts, so its surface is pockmarked with craters, just like the moon. Over its four-year mission, NASA's MESSENGER spacecraft has revealed views of the planet that have challenged astronomers' expectations.

Discovery: Known to the ancients and visible to the naked eye Named for: Messenger of the Roman gods Diameter: 3,031 miles (4,878 km) Orbit: 88 Earth days Venus' southern hemisphere, as seen in the ultraviolet. Credit: ESA Venus The second planet from the sun, Venus is terribly hot, even hotter than Mercury. The atmosphere is toxic. The pressure at the surface would crush and kill you. Scientists describe Venus’ situation as a runaway greenhouse effect. Its size and structure are similar to Earth, Venus' thick, toxic atmosphere traps heat in a runaway "greenhouse effect." Oddly, Venus spins slowly in the opposite direction of most planets. The Greeks believed Venus was two different objects — one in the morning sky and another in the evening. Because it is often brighter than any other object in the sky — except for the sun and moon — Venus has generated many UFO reports.

Discovery: Known to the ancients and visible to the naked eye Named for: Roman goddess of love and beauty Diameter: 7,521 miles (12,104 km) Orbit: 225 Earth days An image of the Earth taken by the Russian weather satellite Elektro-L No.1. Credit: NTsOMZ Earth The third planet from the sun, Earth is a waterworld, with two-thirds of the planet covered by ocean. It’s the only world known to harbor life. Earth’s atmosphere is rich in life-sustaining nitrogen and oxygen. Earth's surface rotates about its axis at 1,532 feet per second (467 meters per second) — slightly more than 1,000 mph (1,600 kph) — at the equator. The planet zips around the sun at more than 18 miles per second (29 km per second).

Diameter: 7,926 miles (12,760 km) Orbit: 365.24 days Day: 23 hours, 56 minutes Related: Mars researchers are focusing both Earth-based and planet orbiting sensors to better understand sources of methane on the red planet. Image Credit: Space Telescope Science Institute Mars The fourth planet from the sun, is a cold, dusty place. The dust, an iron oxide, gives the planet its reddish cast. Mars shares similarities with Earth: It is rocky, has mountains and valleys, and storm systems ranging from localized tornado-like dust devils to planet-engulfing dust storms. It snows on Mars. And Mars harbors water ice. Scientists think it was once wet and warm, though today it’s cold and desert-like. Mars' atmosphere is too thin for liquid water to exist on the surface for any length of time. Scientists think ancient Mars would have had the conditions to support life, and there is hope that signs of past life — possibly even present biology — may exist on the Red Planet.

Discovery: Known to the ancients and visible to the naked eye Named for: Roman god of war Diameter: 4,217 miles (6,787 km) Orbit: 687 Earth days Day: Just more than one Earth day (24 hours, 37 minutes) Related: Close-up of Jupiter's Great Red Spot as seen by a Voyager spacecraft. Credit: NASA/JPL-Caltech Jupiter The fifth planet from the sun, Jupiter is huge and is the most massive planet in our solar system. It’s a mostly gaseous world, mostly hydrogen and helium. Its swirling clouds are colorful due to different types of trace gases. A big feature is the Great Red Spot, a giant storm which has raged for hundreds of years. Jupiter has a strong magnetic field, and with dozens of moons, it looks a bit like a miniature solar system.

Discovery: Known to the ancients and visible to the naked eye Named for: Ruler of the Roman gods Diameter: 86,881 miles (139,822 km) Orbit: 11.9 Earth years The shadow of Saturn's moon Mimas dips onto the planet's rings and straddles the Cassini Division in this natural color image taken as Saturn approaches its August 2009 equinox. Credit: NASA/JPL/Space Science Institute Saturn The sixth planet from the sun is known most for its rings . When Galileo Galilei first studied Saturn in the early 1600s, he thought it was an object with three parts. Not knowing he was seeing a planet with rings, the stumped astronomer entered a small drawing — a symbol with one large circle and two smaller ones — in his notebook, as a noun in a sentence describing his discovery. More than 40 years later, Christiaan Huygens proposed that they were rings. The rings are made of ice and rock. Scientists are not yet sure how they formed. The gaseous planet is mostly hydrogen and helium. It has numerous moons .

Discovery: Known to the ancients and visible to the naked eye Named for: Roman god of agriculture Diameter: 74,900 miles (120,500 km) Orbit: 29.5 Earth years Day: About 10.5 Earth hours Related: Near-infrared views of Uranus reveal its otherwise faint ring system, highlighting the extent to which the planet is tilted. Credit: Lawrence Sromovsky, (Univ. Wisconsin-Madison), Keck Observatory Uranus The seventh planet from the sun, Uranus is an oddball. It’s the only giant planet whose equator is nearly at right angles to its orbit — it basically orbits on its side. Astronomers think the planet collided with some other planet-size object long ago, causing the tilt. The tilt causes extreme seasons that last 20-plus years, and the sun beats down on one pole or the other for 84 Earth-years. Uranus is about the same size as Neptune. Methane in the atmosphere gives Uranus its blue-green tint. It has numerous moons and faint rings.

Discovery: 1781 by William Herschel (was thought previously to be a star) Named for: Personification of heaven in ancient myth Diameter: 31,763 miles (51,120 km) Orbit: 84 Earth years Neptune’s winds travel at more than 1,500 mph, and are the fastest planetary winds in the solar system. Credit: NASA/JPL Neptune The eighth planet from the sun, Neptune is known for strong winds — sometimes faster than the speed of sound. Neptune is far out and cold. The planet is more than 30 times as far from the sun as Earth. It has a rocky core. Neptune was the first planet to be predicted to exist by using math, before it was detected. Irregularities in the orbit of Uranus led French astronomer Alexis Bouvard to suggest some other might be exerting a gravitational tug. German astronomer Johann Galle used calculations to help find Neptune in a telescope. Neptune is about 17 times as massive as Earth. Discovery: 1846 Pluto and its moons orbit the sun near the edge of our solar system.

Learn all about Pluto's weirdly eccentric orbit, four moons and more in this Space.com infographic . Credit: SPACE.com/Karl Tate Pluto (Dwarf Planet) Once the ninth planet from the sun, Pluto is unlike other planets in many respects. It is smaller than Earth's moon. Its orbit carries it inside the orbit of Neptune and then way out beyond that orbit. From 1979 until early 1999, Pluto had actually been the eighth planet from the sun. Then, on Feb. 11, 1999, it crossed Neptune's path and once again became the solar system's most distant planet — until it was demoted to dwarf planet status. Pluto will stay beyond Neptune for 228 years. Pluto’s orbit is tilted to the main plane of the solar system — where the other planets orbit — by 17.1 degrees. It’s a cold, rocky world with only a very ephemeral atmosphere. NASA's New Horizons mission performed history's first flyby of the Pluto system on July 14, 2015.

[Related: New Horizons' Pluto Flyby: Latest News, Images and Video ] Discovery: 1930 by Clyde Tombaugh Named for: Roman god of the underworld, Hades Diameter: 1,430 miles (2,301 km) Orbit: 248 Earth years NASA Solar System Exploration: Dwarf Planets Planet Nine Planet Nine orbits the sun at a distance that is 20 times farther out than the orbit of Neptune. (The orbit of Neptune is 2.7 billion miles from the sun at its closest point.) The strange world's orbit is about 600 times farther from the sun than the Earth's orbit is from the star. Scientists have not actually seen Planet Nine directly . Its existence was inferred by its gravitational effects on other objects in the Kuiper Belt, a region at the fringe of the solar system that is home to icy objects left over from the birth of the sun and planets.

Question: Which planet is the densest in the Solar System?
Answer: Earth